The present invention is directed to pressure-sensitive-adhesive constructions containing releasable heat-sensitive materials, particularly to the methods for their production.
There are contained in the pressure-sensitive adhesive of the construction to which the invention relates, heat-sensitive materials which are volatile and/or temperature-sensitive. The pressure-sensitive-adhesive structure enables controlled release of the entrained materials. Materials to be included range from medicaments to fragrances to repellants.
Pressure-sensitive adhesives are normally formed by bulk, solvent or emulsion polymerization. In the application of such pressure-sensitive adhesives to a substrate, heat is required to achieve a useful product. In the case of a bulk adhesive, the adhesive is normally applied to a substrate by hot-melt techniques. In the case of a solvent-based pressure-sensitive adhesive, the adhesive layer is formed, after being cast onto a substrate, by evaporation of the solvent through application of heat. The same is true where the adhesive layer is cast as a coatable emulsion.
A definite body of art has aligned itself towards the controlled release of medicaments. This art is called "transdermal delivery systems." U.S. Pat. Nos. 3,598,123 and 3,731,683, both to Zaffaroni, disclose the use of reservoirs, such as microcapsules, as the agent to control the release of medicaments from a pressure-sensitive adhesive contained on a carrier such as a bandage.
U.S. Pat. No. 3,632,740 to Robinson et al discloses the inclusion of corticosteriods in pressure-sensitive adhesive bases.
U.S. Pat. No. 3,699,963, also to Zaffaroni, pertains to the controlled release of a drug to the oral mucosa, again through the use of microcapsules from a pressure-sensitive adhesive.
U.S. Pat. No. 4,073,291 to Marvel et al pertains to the inclusion of tretinoin in a pressure-sensitive adhesive for control of acne.
While U.S. Pat. No. 4,336,243 to Sanvordeker et al pertains to a silicone-matrix pad which contains, and which controls administration of, nitroglycerin, U.S. Pat. No. 4,421,732 to Komuro et al also pertains to a pressure-sensitive tape containing nitroglycerin, the adhesive being rubber-base and the nitroglycerin being dissolved therein.
Scopolamine is stored for delivery in one construction consisting of four layers. To an impervious bonding layer there are added, in sequence, a drug reservoir of scopolamine, mineral oil, and polyisobutylene; a microporous polypropylene membrane which controls the rate of delivery of scopolamine; and, finally, an adhesive layer of mineral oil, polyisobutylene and scopolamine. After removal of a peel strip, the adhesive is applied to the skin behind the ear, and protects against motion sickness for up to three days.
Other than by the use of the microspheres or membranes, or perhaps concentration of the contained agent, means to modify the system for control of the release of the contained agent from the adhesive, are not disclosed in this body of art.
The present invention is directed to curing the deficiencies of the prior art, to provide a broad-based system for enabling controlled release of agents contained in adhesives and related strips, particularly to the retention and controlled release of thermally-sensitive materials, i.e., materials which have a relatively low vapor pressure and which would be lost upon application of heat, or would undergo undesirable thermal alteration by application of heat.